This relates generally to graphics processors and particularly to handling instructions that perform the addition of results of multiple multiplications.
A number of equations must be evaluated in graphics processors despite the fact that they involve several multiplications and additions of multiplied terms. Examples of such compound equations include the plane equation, the dot product, and linear interpolation. For example, the plane equation has the form A*X+B*Y+C, where A, B, C, X and Y are floating point numbers.
The entities A*X, B*Y and C, each involve one “term” instruction. Thus the plane equation is an example of an equation with three term instructions. An example of an equation with four term instructions is the dot product DP4 calculation.
Precision is important, particularly in commonly used equations. In addition it is desirable to reduce the power consumption of instruction execution and increase throughput.